In Pennsylvania, eastern subterranean termite swarms usually happen from February to June. Winged reproductives gather near doors and windows, and the wings they shed are often the only sign that a colony is nearby. Older Philadelphia houses with timber framing deserve a closer look.
Key takeaways
- Eastern subterranean termite swarms usually occur in Pennsylvania between February and June, according to Penn State Extension.
- A swarm is a colony's reproductive flight. It shows that termites are nearby, but it does not show how much wood is affected.
- Shed wings near a window, a door or a cellar sill are often the only evidence most people find, and they are worth photographing.
- Do not spray a swarm or wipe the area clean before a technician sees it. Keep a sample and photograph the scene.
- A structure inspection is what shows whether a colony is in the building, and a swarm alone does not answer that question.
What is a termite swarm?
A termite swarm is a group of winged reproductive termites leaving a colony to pair and start new colonies. It is a short event, and the insects are weak fliers that drop their wings soon after landing. The swarm does not show how large the colony is or how much wood it has reached.
Eastern subterranean termites live in soil and reach wood through mud tubes they build along foundations and masonry. Swarming is the stage when the colony sends out winged adults to find mates and new nesting sites. The insects you see flying are the reproductives, not the workers that eat wood.
Swarmers are often seen near windows, doors, light fixtures and the edges of rooms, because they are drawn to light and gather where they land. Swarmers have four wings of nearly equal length, and they shed them soon after landing, which is why small piles of wings appear on sills and in corners.
A swarm can come from a colony in the soil next to the house, in a neighbor's yard or from wood inside the building's footprint. A technician finds the source by inspection, not by the swarm alone, and the inspection is where the real answer comes from.
When should I expect swarms in Philadelphia?
In Pennsylvania the usual swarm window runs from February to June. Warm, humid days after rain are when swarms are most often seen, and the exact date changes from year to year with the weather.
The swarm window is a guide, not a calendar. A warm spell in February can bring an early swarm, and a cold spring can delay one. The termite control and termite inspection services are timed around the window, not around a fixed date.
Philadelphia's climate is humid for much of the year. National Weather Service normals for 1991 to 2020 put the January average high near 41 degrees Fahrenheit and the July average high near 88. Those large swings explain why spring swarms are better timed by temperature than by the date on a calendar.
A swarm in May falls within the usual window. A swarm in late summer is outside the usual pattern, and a technician should look at it, because the insect may be something else. The Philadelphia pest calendar lists the rest of the year's pests for comparison.
How do I tell a termite swarm from flying ants?
Termite swarmers have straight antennae, a thick body and four wings of nearly equal length. Flying ants have elbowed antennae, a narrow pinched waist and front wings longer than the hind wings. Matching these features is the quickest way to tell them apart.
Look at the antennae first. Termite antennae are straight, like beads on a string. Ant antennae are bent at an elbow. Then check the waist: an ant has a pinched, narrow waist, while a termite's body is broad from the head through the abdomen.
Wings differ too. Termite wings are about equal in size and are shed after landing, leaving fragments on the sill. Flying ant wings are unequal, with the front pair larger, and ants do not usually shed their wings in the same piles near a window.
If you cannot tell, collect a few insects in a sealed container or on tape, photograph them beside a coin and show them to a technician. A correct identification decides whether the next step is an inspection or a different kind of pest control, and the ant control service covers the ant side.
What should I do when I see a swarm?
Photograph the swarm and the wings, collect a few specimens and do not spray or sweep the area clean first. Call a technician for an inspection, and say where the swarmers were found, because that tells the technician where to look.
Take photographs of the insects and the wings with a coin for scale. Save a few insects in a sealed container or tape them to paper. Write down the date, the room and whether they were near a window, a door, a light or a basement, because the location is often the first clue to the colony's position.
Do not spray the swarm with household insecticide. The spray kills a few insects, does not reach the colony and can damage the surface where the evidence sits. Vacuuming the wings is also a poor idea, because the wings are part of the evidence a technician needs.
Ask for a structure inspection. The inspection looks at the foundation, the sill plates, the cellar walls, the wood near the soil and any mud tubes that run along masonry. A swarm can start the conversation, and the inspection answers the question.
Why do older Philadelphia houses deserve a closer look?
Many older houses in the city have timber framing, masonry foundations with gaps, and cellars in contact with soil. Those conditions give termites soil access and hidden wood, so a swarm in an older house is a reason to inspect the cellar and framing closely.
Much of Philadelphia's housing was built before 1940. Rowhouses in older blocks often have wood joists and sills set into masonry walls, cellars with dirt floors or little ventilation, and porches attached to the main structure. Those features are not proof of termites, but they give a colony an entry point and a long concealed path to wood.
Look for points where wood meets soil or masonry, such as sills, porch posts and the framing near a front step, and check the foundation walls for mud tubes. A technician uses probes and moisture readings and may open a small area to see the damage behind a finish. The Queen Village and Bella Vista page covers the older blocks there.
Renovations change the picture. A finished cellar, a new deck or a rear addition can create new paths from soil to wood, and a moisture problem from a downspout can make wood more attractive to termites. Tell the technician about recent work, because it changes where to look first.
What does a termite inspection look for?
A termite inspection looks for the signs of an active colony, the points where wood meets soil or masonry, and the moisture conditions that help a colony thrive. The inspection is the step that decides whether a swarm reflects a colony inside the building.
The technician checks the cellar or crawlspace first, because it is where soil meets wood most often. Looking for mud tubes on foundation walls, damp or softened wood, and wood debris on the floor are the core checks. Probing sills and joists with a tool shows whether the wood is hollow or soft.
Above ground, the inspection covers window and door frames, porch posts, the framing near a front step and any wood that touches the masonry or the soil. A technician also notes plumbing leaks, downspouts that discharge against the wall, and stacked firewood or lumber close to the house, because moisture and cellulose draw termites.
A good inspection records what was checked and what was not. Ask the technician to name any area that could not be reached, such as a finished wall or a closed crawlspace, and to explain how that gap might be closed. An honest list of limits is more useful than a report that claims to see everything.
How do termite inspections fit into the season?
An inspection is most useful before the swarm season begins, or as soon as swarmers are seen. Ask for a written report that lists the findings, the areas inspected and any recommendations, and keep it with your house records.
A pre-season inspection gives you a baseline. It shows where the foundation and framing are in contact with soil, and it notes conditions that tend to attract termites, such as wood debris, leaks and stored materials against the wall. A technician can point out what to remove or correct before the swarm window opens.
Ask whether the inspection covers the basement, crawlspace, interior walls and exterior foundation, and whether it includes attached structures such as a porch or garage. Ask what the report will say if no activity is found. Confirm that the company's applicators are certified and that the business holds the Pennsylvania Department of Agriculture licence, because the state licenses pest control businesses and certifies applicators.
Ask for the written report in advance and compare future inspections with it. The report is also useful if you sell the house, plan a renovation or need to show a buyer or lender what was checked and when.
Frequently asked questions
Is a termite swarm always a sign of damage?
No. A swarm shows that a colony of reproductive termites has flown out, which means a colony exists nearby. Damage depends on the colony and the wood, and only an inspection can show whether the structure is affected.
What do termite wings look like after they are shed?
They are thin, clear and about the same size front and back. They often appear in small piles or scattered on a sill or near a window, and they can be mistaken for dust or flakes of paint.
Can I treat termites myself?
Household products are not a substitute for an inspection. A technician must find the colony and select the method. Spraying can disturb the colony and hide the evidence the inspection needs.
Do termites only show up in spring?
Swarming is most visible in spring, but termites are active year round in soil and wood. A swarm is one visible stage, and the colony can be present outside the swarm season.
Does homeowners insurance cover termite damage?
Termite damage is usually excluded from standard homeowners policies. Read your policy and ask the insurer, and see the pest damage and insurance claims guide for the general pattern. This answer is not a coverage decision.
Sources
- Penn State Extension - Eastern subterranean termites
- National Weather Service - Philadelphia climate normals
This guide is general information for Philadelphia County homeowners, not a substitute for an on-site inspection. Prices are estimates. See our disclaimer.